Sound construction and design practice, building codes, regulation and legislation require a number of measures to protect those who work, inhabit and visit buildings and other structures. A primary fire safety improvement required by government and industry regulation, is the use of EXIT signs to indicate egress routes. Among other requirements, exit signs must clearly direct those in flight to the nearest exit during a fire or other emergency.
A simple "EXIT" message can be provided directly above the egress from the building or, where the egress is located away from the optimum position from which the sign can best be viewed, an "EXIT" message is normally coupled with a directional indicator that points toward the exit. Because numerous exit signs may be deployed within a single structure, it is critical that the exit sign and all its components (including the directional indicator) be of low cost, highly durable, and easily installed within the structure.
To accomplish these ends, exit signs have been developed that feature directional indicators or arrows surrounding both sides of the exit sign, with knockouts capable of being removed from the face of the exit sign in order to allow the installer to choose in which direction the exit sign directional indicator should point. For instance, U.S. Pat. No. 3,931,689 to Shine discloses an exit sign with removable arrowheads that have punched or scored portions to allow the installer to select one arrowhead and remove it. Another, almost identical, removable arrowhead surrounded by punch out areas is disclosed by U.S. Pat. No. 5,018,290 to Kozek, et al. However, the scoring about the edges of the arrowhead remaining in place will likely allow significant light to leak through the scoring, possibly to misdirect people away from the location of the exit.
Moreover, while such knockouts make deploying an exit sign easier, they do not allow the arrowheads to be reinserted into the sign in the event that an installer mistakenly removes the wrong arrowhead or the exit sign is redeployed to another area in which the directional indicator points in the wrong direction. Even arrowheads that can be so replaced will often fall behind the face of the exit sign and can only be retrieved with difficulty. For instance, it is known to provide a triangular cover that inserts from behind the exit sign cover and is retained in place by posts positioned about the perimeter of the aperture within the exit sign cover into which a triangular insert is placed. However, pressure upon the front of the triangular insert may cause the posts to release the insert, resulting in its falling into the exit sign. To reinsert the triangular insert requires the exit sign to be removed, and/or its cover taken off and the triangular insert retrieved and replaced, a sometimes laborious and time consuming procedure.
Other exit signs likewise employ covers for directional indicators that may be installed only with laborious procedures. Thus, U.S. Pat. No. 4,355,479 to Thornton discloses an exit sign that allows the installer to select between one of two directional arrowheads by sandwiching an opaque strip between (1) a stencil defining the word "EXIT" and two adjacent arrowhead shaped apertures and (2) a border strip. Yet properly positioning the opaque strip and then installing the entire assembly is extremely time consuming. Similarly, U.S. Pat. No. 3,665,626 to Lund, et al. discloses a cover with a rectangular hole behind which is a mask having arrowheads pointing in various directions, the mask being adjustable to move a left or right pointing arrowhead into the area directly behind the rectangular hole of the cover to thereby provide a direction indicator. The mask-like means may fail to fill the hole completely, and thus significant light leakage may occur. Furthermore, given the number of exit signs installed in a modern office building, retail store or other significantly sized structure, ease of installation is a necessity in order to minimize labor costs. Neither the Thornton nor Lund, et al. patents disclose devices which admit of easy and quick installation with a minimum of tools. Moreover, once installed, the Thornton and Lund, et al. devices may be jarred or impacted sufficiently to cause the strip or mask to move and display an incorrect directional indication.
Providing covers that tightly secure to directional indicators and maintain a tight, impervious-to-light-leakage or light-fast fit thus remains a significant problem. For instance, in a blazing or smoke obstructed building, the exit sign's direction indicating arrow may be partially obscured and light leaking from the aperture in which an insert is still in place may suggest the wrong direction to the ultimate disadvantage of those who aim to escape. Accordingly, the National Fire Protection Association ("NFPA") has promulgated a "Life Safety Code" (incorporated herein in its entirety by this reference), as of Feb. 11, 1994, which requires that the directional indicator, preferably chevron-shaped, "be identifiable at a minimum distance of 100 ft. (30 m) under all space illumination conditions." To meet these standards, only an extremely minimal level of light leakage about the edges of the cover of a directional indicator is allowed.
The chevron shape required by new regulations, such as those promulgated by the NFPA, provides a larger illuminated surface area than conventional, triangular shaped arrowhead directional indicators. This follows from the fact that for the same height, the chevron shape will cover twice the area as a triangular directional indicator. With the larger illuminated area, the chevron directional indicator is far easier to make out at a distance or in smoke. The downside, primarily for purposes of attachment to the cover, is that the wings of the chevron are long and can thus bend. Accordingly, the chevron, with its larger surface area and greater potential for bending, demands a new approach to being fastened integrally, but easily and tightly, within the cover.
Notwithstanding these requirements and regulations, many conventional replaceable arrowheads simply do not fit sufficiently tightly within their arrowhead shaped apertures so as to preclude light leakage around the edges of the fit between even the conventional arrowhead cover and the arrow aperture. A prime example is the replaceable arrowhead disclosed in U.S. Pat. No. 5,247,756 to Johnstone. Johnstone discloses "a cover [that] is provided with a tongue arranged on its rear surface and projecting from its directional point so as to reside in the stencil notch when . . . inserted. A snap rail is located on the arrow cover edge opposite to its directional point and shaped to mate with the bead of a corresponding edge of the arrow shaped void." The cover is inserted by sliding the tongue into its matching notch and pressing down.
The Johnstone structure aims to provide an arrow which may easily be inserted into the cover from the outside of the sign, but which prevents the worker from inadvertently pushing the cover into the sign and wasting time trying to retrieve it. It does this with the tongue/notch interface on the nose of the arrow. The tongue must first be slid into the notch, thus precluding pushing the arrow into the interior of the fixture, before the back of the arrow is snapped into place. Unfortunately, this "slide `n` snap" structure precludes a light-fast, secure fit.
Although the Johnstone device purports "to provide a snug fit against the bead and a closed seal to the passage of light when inserted in the stencil void," because the only points of connection are the tongue at the arrow point and the snap rail in the area directly opposite, the fit is not snug around the sides and light accordingly leaks out of the improper fit. Furthermore, the arrow cover is thinner than the exit sign cover to which it is attached and will therefore expand, contract or deform at a different rate than the exit sign cover, which movement creates a loose fit. The loose fit is exacerbated by a pressure pad that prevents the tongue of the arrow cover from resting firmly in its notch and essentially acts as a fulcrum upon which the tongue can oscillate back and forth as the inadequately secured ends of the triangle move within the cover.
These problems would become more pronounced if chevron-shaped directional indicators, which normally each have two long, relatively thin legs, were used rather than the triangular arrowheads disclosed by Johnstone. With chevron-shaped indicators, there is no triangular base to attach to the cover and the legs are therefore more likely to be imperfectly secured and leak light about their edges.
Accordingly, a need arises for a chevron-shaped directional indicator cover that can be fastened firmly into the directional indicator of an exit sign to provide a tight, light-fast fit. Such a cover must continue to maintain the tight, light-fast fit over a long period of time and endure a variety of hostile environmental conditions, including innumerable temperature and humidity excursions, point impacts caused by personnel within the building jostling the exit sign or from maintenance of the exit sign wherein the cover is constantly removed and subject to impact, the inadvertent provision of over powered (and therefore hotter) lamps or even attacks by vandals or a fire. Yet the cover must be installed correctly and competently with a minimum of effort and in minimum time by those who may bring only modest skills and few tools to the task.